1. Field of the Invention
The present invention relates to a light exposure apparatus, and more particularly, to a light exposure apparatus suitable for fabrication of a liquid crystal display (LCD) and capable of preventing static electricity thereon.
2. Discussion of the Related Art
Until recently, cathode-ray tubes (CRTs) have been utilized as display devices. Presently, much effort is being expended to study and develop various types of flat panel displays, such as LCD devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as substitutes for the CRTs.
The flat panel display usually includes a light emitting layer or a light polarizing layer on at least one transparent substrate. There is an active matrix type flat panel display, which includes a plurality of thin film transistors (TFTs) arranged in a matrix manner. This active matrix type flat panel display is becoming widely utilized because of its high resolution and high ability of displaying moving images.
The flat panel display has a multi-laminated structure, which is fabricated through the repetition of a thin film-depositing process, a photolithography process and a thin film-etching process. The photolithography process transfers patterns of a photo-mask to the deposited thin film on a substrate by depositing a photoresist on the deposited thin film on the substrate, aligning the substrate and exposing the deposited thin film on a light. In particular, the light-exposing process is performed utilizing a light exposure apparatus.
FIG. 1 is a schematic plan view of a light-exposing apparatus 100 according to the related art. As shown in FIG. 1, the light exposure apparatus 100 includes a chuck 110, a light source 160 and a photo-mask 150. A substrate 130, on which a thin film 131 and a photoresist layer 140 are formed, is placed on the chuck 110. The chuck 110 supports the substrate 130 during a light-exposing process. Also, the chuck 110 includes plurality of lift pins 120 that are able to move up and down to load and unload the substrate 130. The light source 160 emits a UV (ultra-violet) light toward the substrate 130. The photo-mask 150 has predetermined patterns selectively transmitting and blocking the emitted light from the light source 160. Accordingly, the photoresist layer 140 on the chuck 110 is exposed to the UV light that is emitted from the light source 160 and passes through the photo-mask 150. Then, the photoresist layer 140 is developed to form a photoresist pattern, by which the thin film 131 is patterned.
FIG. 2 is a schematic plan view of the chuck 110 for the related art light exposure apparatus 100. As shown in FIG. 2, a recess portion 116 is formed in a center portion of the chuck 110. Corners of the recess portion 116 are extended along two diagonal lines of the recess portion 116. A plurality of lift pins 120 are symmetrically arranged in the recess portion 116. Specifically, there are four lift pins 120 arranged at the extended four corners along two diagonal lines. The plurality of lift pins 120 are able to move up and down to load and unload the substrate 130. A plurality of vacuum holes 118 are arranged in an upper surface of the chuck 110. When the substrate 130 is loaded on the upper surface of the chuck 110, the vacuum holes 118 are inhaled to be under vacuum so that the substrate 130 can be tightly attached to the upper surface of the chuck 110.
FIG. 3A is a schematic cross-sectional view illustrating the related art chuck 110 and the substrate 130 when the lift-pin 120 is in an up position, and FIG. 3B is a schematic cross-sectional view illustrating the related art chuck 110 and the substrate 130 when the lift pin 120 is in a down position. As shown in FIGS. 3A and 3B, when the lift pin 120 is in the up position, a robot places the substrate 130 on the lift pin 120. Then, the lift pin 120 moves down to the down position thereby placing the substrate 130 on the upper surface of the chuck 110. After that, the vacuum hole 118 (of FIG. 2) is inhaled to be under vacuum so that the substrate 130 can closely adhere to the upper surface of the chuck 110.
When the substrate 130 adheres to the upper surface of the chuck 110, the light emitted from the light source 160 (of FIG. 1) and passing through the photo-mask (150 of FIG. 1) irradiates the photoresist layer 140 (of FIG. 1) to conduct a light-exposing process. After the light-exposing process is completed, the lift pin 120 moves up to the up position so that the robot holds up and transfers the substrate 130 for a following process.
According to the related art, however, when the lift pin 120 is in the up position as shown in FIG. 3A, peripheral portions of the substrate 130 are bent downward. Therefore, when the lift pin 120 moves down to load the substrate 130 on the chuck 110, the bent peripheral portions of the substrate 130 contact the upper surface of the chuck 110 earlier than the rest portions of the substrate 130, thereby generating frictions between the peripheral portions of the substrate 130 and the upper surface of the chuck 110. Due to the frictions, the chuck 110 has positive electrostatic charges at its edge portions. Further, the positive electrostatic charges remain in the edge portions of the chuck 110. For this reason, when the lift pin 120 moves up to the up position to unload the substrate 130, a spark discharge is generated due to static electricity at edges of the substrate 130, in particular at corners of the substrate 130. The discharge increases a burden on the lift pin 120, thereby causing operational errors of the light exposure apparatus 100 (of FIG. 1).